If I understand your question, the answer is no, banking or borrowing are final transactions & cannot be undone.
As for why it happens, I'm a perfect example. I booked our December trip in Jan. at our home resort. Then I bought a second contract which had points I needed to use and so I booked my new home resort w/ those points (plus a few more) for half of the time of my original booking & canceled that part thus freeing up those points - so the points are a bit of a mess, but I'll use them anyway ultimately, c'est la vie, so yes plans change.
W/ people selling, it may be they are selling for unplanned reasons which also caused them to cancel future vacations.
Personally, when I was shopping for a
DVC contract, borrowed or banked points into the current use year had little value to me unless I would have been able to use them prior to the expiration of the use year they were in. And by use I mean both had a planned vacation & would have access to them before the 7 month booking window thus having likely availability at that resort.